Now war is again threatening Assyrian culture and language in its native land.

Thousands of Assyrians have fled Iraq since the U.S. invasion. Mr. Samow’s relatives are scattered across Canada, Australia, Denmark, New Zealand, Greece, Holland, England, Sweden and Germany. Other Assyrians are refugees in Syria, Jordan, and inside Iraq — not knowing whether they can return to cities and towns carved into Sunni or Shi’ite enclaves.

“My children speak my language, but what about my grandchildren?” said Mr. Samow from his home in Modesto. “If there are no Assyrians left in Mesopotamia, how will our culture live?”

Successive waves of Assyrians have landed here in California’s Central Valley, beginning with those who fled a massacre by Turks near the end of World War I.

They were joined by families who escaped Iran when an Islamic revolution overthrew the monarchy in 1979, then by new arrivals escaping the first Gulf War, when Mr. Samow, whose hometown is near Mosul, Iraq, came here with his family. An Assyrian community also thrives in Chicago.

But with their numbers now dangerously low in the region where Iran, Iraq and Turkey meet, Assyrians here fear the current wave of migration could mark their end. Community leaders in the United States are working to support Assyrians back home.

The Assyrian American Civic Club of Turlock is housed in a fortresslike hall decorated with winged bulls that have human heads — a traditional Assyrian protective figure known as a lamassus. An old map on the wall shows population centers that no longer exist.

“Once, most villages in that area were Assyrian,” said the club’s president, Fred Betmaleck, who is Iranian-Assyrian. “Now there are very few left.”

The club works to keep Assyrian culture alive by hosting a radio station that plays Assyrian music and carries community news and holds festivals, such as the Assyrian New Year’s celebration known as Kha-b-Nissan, in the spring.

Members also raise money through dances and raffles to help Assyrians who remain in Iraq.

“We try to help them stay there as much as possible, because when you leave, you never go back,” said Mr. Betmaleck. “We encourage them not to come, but when there’s persecution, what can you do?”

For Mr. Samow, staying was too risky.

He and his wife took their seven children — the youngest a 1-year-old whom Mr. Samow strapped to his back — on a dangerous hike across the rugged snow-covered mountains between Iraq and Turkey.

He spent all the money he had saved from his job as a construction contractor to smuggle his family to the dirt-floor tents of a Turkish refugee camp, then to Istanbul. They spent a year and a half in Greece until they applied for asylum with Red Cross help and were accepted into the United States in December 1992.

Now, 15 years and another Iraq invasion later, the family is safe, but they worry about relatives back home, and about the Assyrian future.

“We feel this could be the end of a people who have survived since Babylonian times,” said Zack Samow, 34, Isaac’s oldest son. “This could be the wave that pushes Assyrians out of their homeland for good.”

As cities and towns are reshaped at gunpoint into homogenized Sunni, Shi’ite or Kurdish territory, groups without their own militias or political power are left vulnerable to attacks, said Nina Shea, director of the Hudson Institute’s Center for Religious Freedom and a member of the U.S. Commission on International Religious Freedom.

The priest in Isaac Samow’s hometown of Telkaif disconnected his phone to stop the barrage of threats, the family said.

Assyrian Christians — among the first converts to Christianity — and other ethnic and religious minorities have been particularly hard-hit by the sectarian violence, she said. Among those leaving are Jews; Sabean-Mandeans, who follow John the Baptist; Yazidis, ethnic Kurds whose religion precedes Christianity and Islam; Baha’i and Iraqi Turkmen, Ms. Shea said.

They might dress differently from their Muslim neighbors, speak other languages and pursue businesses that make them stand out — selling liquor, for example. In addition to a construction business, Mr. Samow ran three eating and drinking establishments in Iraq.

Many speak English, and work as translators means they are also often seen as siding with the United States, said Bill Frelick, refugee policy director for Human Rights Watch.

“They’re not just being hunted down because of their religious identity,” he said. “Many of them are regarded as being pro-Western.”

Their absence could allow the region to become less tolerant as it loses the diversity that has characterized it for centuries. And that could have long-term geopolitical consequences, Ms. Shea said.

“It’s a profound loss,” she said. “These populations have lived together for a long time, but if this continues, it will not be a plural society any more. It’ll be devoid of non-Muslims.”